A continuation of a program of research is proposed, to investigate sensory and perceptual processes in spoken communication. The research focuses on the functions that integrate the diverse acoustic components of a speech signal and establish its perceptual coherence. Although many accounts of the normal listener seek to explain the perceptual analysis of speech signals, the present proposal is concerned with a more fundamental processes by which the perceiver finds and follows a speech signal within sensory activity. The primary hypothesis motivating the studies comes from research on sinusoidal replicas of utterances, synthetic acoustic signals that imitate the time-varying properties of speech without also producing short-time spectra typical of natural vocal sounds. These studies have shown that perceivers recognize phonetic properties carried by sinewave replicas of utterances through sensitivity to speechlike changes in an acoustic pattern, superseding the absence of speechlike acoustic details in the fine grain. Four projects comprising twelve experiments are proposed for the coming five years. The research includes a set of studies to expose the precise characteristics of sensitivity to spectrotemporal variation, independent of specific acoustic form; a set of studies to determine the contribution of auditory mechanisms when phonetic organization is imposed on a sinewave pattern; a set of intelligibility studies, to determine the capacity of spectrotemporal variation for conveying the attributes of consonants; and a set of experiments to identify the organizational factors operating in spontaneous speech. Together the investigations will elaborate fundamental processes of detecting and maintaining perceptual coherence, and will offer new evidence of the perceptual accommodations to the variegated acoustic manifestations of speech. Research on the basic sensory and perceptual mechanisms of spoken communication provides essential benchmarks for evaluating the perceptual effects of disease, and will play a role in creating therapeutic accommodations for loss or failure of perceptual resources.